The present invention relates generally to the configuration of a cellular communication network and, more particularly, to a method of self-configuration of parameter settings for a cellular communication network.
In a mobile communication network, the coverage area of the network is divided into a plurality of cells. Conventionally, the configuration of cells and the assignment of certain parameters are set during cell planning and remain static once the system is deployed. As an example, frequencies may need to be assigned to the cells in a manner to reduce interference between cells. This requirement usually means that the same frequency is not reused in neighboring cells. As another example, the cells may be assigned locally unique reference signals (RSs), which are used by the mobile terminal to identify the cells and synchronize to the network.
The assumption that the network topology will remain static once a system is deployed is no longer true. It is now common for cells to be added or subtracted from a network after the system is deployed. For example, pico cells or other low power cells may be deployed in some areas of the network in order to improve coverage. Also, home base stations may be deployed in areas where network coverage is already provided. As new cells are added or subtracted, a different set of neighbor cell relationships is created.
Some mechanism is needed in order to prevent parameter conflicts between neighboring cells when new cells are deployed. For example, a new cell should not be assigned frequencies or RS patterns that conflict with existing assignments. Conventionally, the network administrator can manually assign parameters to the new cells in order to avoid conflicts. However, this is becoming increasingly more difficult as the number of cells in the network increases. In some cases, the network administrator must reconfigure existing cells in order to avoid conflicts. The cell planning that precedes the deployment of new cells can therefore be costly and time-consuming.
One way to simplify deployment of new cells is to make the network self-configuring in as many aspects as possible. U.S. patent application Ser. No. 13/072,496 filed Mar. 25, 2011 which is incorporated by reference herein in its entirety, discloses a general framework for updating system parameters when new cells are deployed. This patent application describes a distributed parameter update procedure based on the exchange of impact functions between neighboring cells. An impact function is a function describing how changes in a parameter setting of a first cell will affect a neighboring cell. When a parameter setting is updated by a cell, the cell exchanges impact functions with its neighboring cells. After the exchange of impact functions, the updating cell can compute a new parameter setting that minimizes the cumulative impact on its neighboring cells. A similar technique is used in other cells, so that as a whole the system gradually converges to an optimum or near optimum result.
The technique described above can be applied to a wide range of system parameters. In cases where the parameter setting is limited to a finite number of discrete values, the impact function can be easily tabulated and exchanged among cells. For a continuous parameter, such as transmit power, the same formulation can be used only if the parameter is quantized. If the quantization step is too large, quantization error may lead to performance degradation. If the quantization step is too small, the large amount of data to be exchanged among cells may exceed the capacity of the inter-cell connection or incur excessive delay.
Accordingly, there remains a need for a distributed parameter update procedure for updating parameters that can have continuous values.